What is the role of lab testing in the workup of trigeminal neuralgia (TN)?

Updated: Jul 11, 2019
  • Author: Manish K Singh, MD; Chief Editor: Robert A Egan, MD  more...
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Answer

No laboratory, electrophysiologic, or radiologic testing is routinely indicated for the diagnosis of trigeminal neuralgia (TN), as patients with characteristic history and normal neurologic examination may be treated without further workup.

The diagnosis of facial pain is almost entirely based on the patient's history. In most cases of facial pain, no specific laboratory tests are needed. A blood count and liver function tests are required if therapy with carbamazepine is contemplated. Oxcarbazepine can cause hyponatremia, so the serum sodium should be tested after institution of therapy.

Although rarely indicated, appropriate blood work for rheumatic diseases, such as scleroderma (trigeminal neuropathy is reported in up to 5% of patients with this collagen vascular disease) and systemic lupus erythematosus (SLE), should be undertaken in patients with atypical features of facial pain and a systemic presentation of collagen vascular disease. Appropriate blood work includes a sedimentation rate (ESR), antinuclear antibody titer (ANA), double-stranded DNA, anti-Sm antibody, lupus erythematosus cell preparation, and complete blood cell (CBC) count to look for hematologic abnormalities (eg, hemolytic anemia, leukopenia, thrombocytopenia). Particularly in the case of scleroderma, creatinine kinase and aldolase levels may be elevated with muscle involvement. Antibody titers to SCL-86 and SCL-70 may also be present.

In cases with suspected metastatic carcinomatosis, cerebrospinal fluid analysis may confirm the diagnosis. When surgical procedures are contemplated, appropriate and routine preoperative laboratory tests are in order.

In patients older than 60 years, the clinician may first choose to assess the response to a therapeutic trial of medication before considering imaging. A clear relief of pain with carbamazepine or another anticonvulsant confirms the diagnosis of idiopathic trigeminal neuralgia.

Imaging studies are indicated, because distinguishing between classic and symptomatic forms of trigeminal neuralgia is not always clear. Approximately 15% of patients with trigeminal neuralgia (any form) have abnormalities on neuroimaging (computed tomography [CT] scanning and/or magnetic resonance imaging [MRI]). The most common findings are cerebello-pontine angle tumors and multiple sclerosis.


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